The disposable-filter holder of the invention is applicable in particular for pressure filtration. The terms "filter" and "pressure filtration" herein also cover similar procedures such as ultra-filtration, reverse osmosis and plain gravity filtration.
As a rule disposable-filter holders of the above species consist of a plastic, two-part housing of which the two housing halves are joined in pressure-tight manner and are flat and boxy. Such disposable-filter holders comprise an inner, essentially flat cavity which is divided by a filter, illustratively a membrane filter, into an intake-side pressurized chamber and a discharge-side filtrate chamber. The filter is secured in conventional manner against tearing by a filter support formed in the lower housing.
As a rule such disposable-filter holders will be used whenever it is desired to filter small and minute volumes of fluid rapidly, reliably and where called for in sterile manner. They are used especially in labs, for instance when preparing high-purity reagent solutions. Another significant field of application is in medical and pharmaceutical labs.
The multiplicity of such applications requires disposable-filter holders which for constant housing and filter dimensions differ merely by the filter characteristics such as the filter material or its pore size and degree of sterility. Because such disposable-filter holders are mass-produced, they must be coded in simple and reliable as well as in distinctive manner. This differentiation may be carried out for instance by individually coding one or both housing parts, illustratively by dyeing the housing material or by characteristic embossing. The disposable-filter holders which are so coded incur the drawback that in the event of a change in production, the mold type must be changed or the entire injection equipment, including the extruder, must be cleaned because another dye is required.
It is known from the German patent document C 28 37 058 how to make disposable-filter holders of different types but with the same housing. The housing halves of one type which are identical for one size are joined in geometrically or frictionally locking manner with the filter being inserted and then are made gas and pressure tight by an injected plastic sealing ring dyed according to the filter code.
This known disposable-filter holder suffers from the drawback that the colored sealing ring must meet simultaneously the functions of hermeticity and sealing on one hand and on the other of coding. Moreover, this sealing ring must enclose both the upper and the lower housing parts. Further, the injection by means of the dyed ring only can take place after the upper and the lower housing parts have been joined. Accordingly this injection molding must take place on the assembled disposable-filter holder.